Boris Johnson has been hit by the first ministerial resignation since he was fined by police for breaking Covid rules, as the justice minister, David Wolfson, said the prime minister’s actions were “inconsistent with the rule of law”. Lord Wolfson said it would be wrong for “that conduct to pass with constitutional impunity, especially when many in society complied with the rules at great personal cost, and others were fined or prosecuted for similar, and sometimes apparently more trivial, offences.” In a letter posted on Twitter, the Conservative peer added that he had “no option other than to tender my resignation”. Wolfson’s resignation will reignite questions about Johnson’s leadership, coming hours after the Conservative MP Nigel Mills said publicly that he would submit a letter of no confidence in the prime minister. The fallout after Johnson, his wife, Carrie, and the chancellor, Rishi Sunak, were issued with fixed-penalty notices as part of Scotland Yard’s Partygate investigation has been somewhat muted, given the fines were handed out while many MPs are on holiday during recess. But despite some of Johnson’s allies’ attempts to play down the gathering that he was fined for attending by claiming he was only present for nine minutes for people to wish him happy birthday, Wolfson seemed clear that the event broke Covid rules. He wrote in a letter to Johnson on Wednesday afternoon: “Justice may often be a matter of courts and procedures, but the rule of law is something else – a constitutional principle which, at its root, means that everyone in a state, and indeed the state itself, is subject to the law. “It is not just a question of what happened in Downing Street, or your own conduct. It is also, and perhaps more so, the official response to what took place. As we obviously do not share that view of these matters, I must ask you to accept my resignation.” Wolfson said he was proud of helping the government with planned judicial reforms. But he added: “We can only undertake these and other legal reforms at home, and also credibly defend democratic norms abroad, especially at a time of war in Europe, if we are, and are seen to be, resolutely committed both to the observance of the law and also to the rule of law.” In his reply, Johnson said he was “sorry to receive” the letter and thanked Wolfson for his service, highlighting his work with the judiciary during the coronavirus pandemic. The government had “benefitted from your years of legal experience”, Johnson said. Wolfson is the second justice minister to quit under Johnson’s leadership, after the resignation of Lord Keen in September 2020 over the prime minister’s attempt to potentially break international law by overriding parts of the Brexit deal. Steve Reed, the shadow justice secretary, congratulated Wolfson “for taking a principled stand”. But he asked: “What does this mean for the lord chancellor, Dominic Raab, who’s constitutionally charged with upholding the law but is instead condoning law-breaking?” Johnson received and paid his £50 fine on Tuesday, and is said to be being investigated by the Met for attending up to six potentially law-breaking events. He faces the prospect of being issued with further fixed-penalty notices if officers decide other gatherings he was at – including the “bring your own booze” garden party to which more than 100 people were invited – are deemed to have breached Covid rules.